1. Field of the Invention
The present invention relates to a method and system for correcting lens shading, and more particularly, to correcting lens shading of an input image by acquiring a luminance weight value for an edge pixel in each block by partitioning a photographed reference image into a plurality of blocks.
2. Description of the Related Art
In general, an image sensor is a device used for photographing an image by using the properties of a semiconductor that reacts to light. An image sensor is a device in which a pixel senses brightnesses and wavelengths of different lights emitted from subjects, and converts the sensed brightnesses and wavelengths into electrical values. Converting the electrical value into a signal processable level is also the role of the image sensor.
That is, the image sensor is a semiconductor element that converts an optical image into an electrical signal. A charge coupled device (CCD) is an element in which metal oxide semiconductor (MOS) capacitors are positioned extremely close to one another, and electrical charges are stored in and transferred to, the capacitors. A complementary metal oxide semiconductor (CMOS) image sensor is an element that adopts a switching type that sequentially detects an output by using a control signal and a signal processing circuit as a peripheral circuit. The CMOS image sensor is formed using MOS transistors in an amount equal to the number of pixels.
The CMOS image sensor has a large advantage in that it has low-power consumption, and therefore is very useful for personal portable systems such as a cellular phone camera, PC camera and the like. The CMOS image sensor can also be applied for various other purposes in addition to those applicable to the consumer electronics field. For example, CMOS image sensors may also be used in the medical field, the toy field, etc., and the like.
An image sensor generally photographs an optical image of a subject through a lens. A problem is created by the lens in that a lens' shading phenomenon causes change of luminance at an edge portion of a photographed image compared to luminance at a center portion of an image. This shading phenomenon is due to, for example, influence of the lens' shape.
Therefore, the lens shading phenomenon should be corrected in order to acquire a more true image. However, in the prior art, after a luminance weight value is acquired for each of the entirety of the pixels of the image sensor in order to correct the lens shading, a method of multiplying a luminance weight value by each pixel of an input image is used. Since the luminance weight value is calculated for all pixels and stored, a memory having a large capacity is required.